Patterns of covariation in survival rates of British Columbian and Alaskan sockeye salmon (Oncorhynchus nerka) stocks

Abstract

We used a multi-stock comparison to identify spatial and temporal characteristics of environmentally driven sources of variability across four decades in the productivity of 29 sockeye salmon (Oncorhynchus nerka) stocks from British Columbia (B.C.) and Alaska. We examined patterns of covariation among indices of survival rate (residuals from the best-fit stock-recruitment curve) and found positive covariation among Fraser River sockeye stocks (southern B.C.) and, to a greater extent, among Bristol Bay stocks (western Alaska) but no evidence of covariation between these two regions or with stocks of other regions in B.C. and Alaska. This indicates that important environmental processes affecting variation in sockeye survival rate from spawners to recruits operate at regional spatial scales, rather than at the larger, ocean-basin scale. The observed covariation in survival rates of Bristol Bay stocks appears to be due to a combination of both freshwater and, to a greater degree, marine processes. Bristol Bay sockeye stocks showed a dramatic and persistent increase in survival rates coinciding with the abrupt changes in the North Pacific environment in the mid-1970s; however, there was little evidence of a similar response for Fraser River stocks.

Magnitude and Trends in Abundance of Hatchery and Wild Pink Salmon, Chum Salmon, and Sockeye Salmon in the North Pacific Ocean

“…For instance, sockeye salmon from Bristol Bay showed substantial increases in survival rate (measured as recruits per spawner) since the early to mid-1970s, even after correcting for within-stock density-dependent effects related to spawner abundance (Peterman et al 1998(Peterman et al , 2003. Pink salmon populations, even those in Alaska, did not show consistent increases or decreases in recruits per spawner (corrected for within-stock density-dependent effects), but spawners increased after the 1970s for most of those populations (Pyper et al 2001).…”

“…The largest portion of salmon population data on the West Coast of North America came from 120 populations of pink salmon, chum salmon, and sockeye salmon that were previously described by Peterman et al (1998), Pyper et al (2001Pyper et al ( , 2002, Mueter et al (2002b), and Dorner et al (2008), the latter of which includes the original data set through the early 2000s. The database was updated with catch and spawning abundance values from recent regional reports, run reconstructions (Starr and Hilborn 1988;English et al 2006), and data that were not included in those specific populations.…”

Temporal synchrony and variation in abundance of Atlantic salmon (Salmo salar) in two subarctic Barents Sea rivers: influence of oceanic conditions

“…However, correlation analyses are often confounded by problems associated with autocorrelation . To account for autocorrelation in our analyses, we followed the approach outlined by Peterman et al (1998) where corrected degrees of freedom (N* -2) are determined according to the following formula:…”

Declining patterns of Pacific Northwest steelhead trout (Oncorhynchus mykiss) adult abundance and smolt survival in the ocean

“…Thus, it might be expected that they would exhibit lower rates of variation in recruitment and marine survival over time than many marine fishes. However, research shows that marine survival for many Pacific salmonids varies greatly over time (e.g., Kilduff et al 2014;Peterman et al 1998;Pyper et al 2002;Teo et al 2009;Zimmerman et al 2015), though it has not been fully examined across species. With persistent pressures on Pacific salmonids by humans, the increasing threat of climate change, and continued calls for recovery, monitoring population abundance and survival trends over space and time is essential for identifying the factors affecting population dynamics to guide appropriate management and conservation actions (Bisbal and McConnaha 1998;Burke et al 2013).…”